Apparatus for magnetic separation



J. H. WEIS OR MAGNETI C SEPARATION APPARATUS F Filed Jan. 14, 1933 INVENTCR Patented Dec. 1, 1936 PATENT OFFICE APPARATUS FOR MAGNETIC SEPARATION Joseph H. Weis, Scranton, Pa., assignor to Feldspathic Research Corporation, New York, N. Y., a corporation of Delaware Application January 14, 1933, Serial No. 651,677

4 Claims.

This invention relates to a novel apparatus useful in many and various industries to separate pulverulent magnetic from non-magnetic substances with or without preliminary sizing. The

invention provides a magnetic separator especially suitable for use in treating pulverized or comminuted materials whose fineness previously precluded their successful separation on magnetic separators and, at the same time, to provide a sizing apparatus, if desired. Furthermore, there is provided a magnetic separating screen of the greatest possible efiiciency, simple construction, and with low original cost and low maintenance expense. To this end, a closed magnetic circuit is used to magnetize one or more screens, and

the material is fed in direct contact with magnetized screen surfaces of'high flux density, thus providing the most efficient application of the magnetic flux to the minute particles. The

screens are preferably vibrated, and periodically are demagnetized to discharge the magnetic material away from the non-magnetic material previously passed through.

The invention will be described in connection with the accompanying drawing, in which:

Fig. 1 is a vertical section through a magnetic separator embodying the invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a vertical section illustrating a modification of the invention; and

Fig. 4 is a cross-section on line 4-4 of Fig. 3.

The separator shown in Figs. 1 and 2 comprises a plurality of superposed screens I to 5 inclusive made of magnetic material and preferably mounted parallel to each other in a frame or box having two opposite sides 6 and l of magnetic material such as iron or steel and the other two opposite or connecting sides 8 and 9 of nonmagnetic material such as brass or bronze.

The screens may consist of sheet metal having holes punched or otherwise'formed therein, or may consist of wire mesh cloth, the screens in any case being stretched tightly to permit them to vibrate and being of the smallest possible 45 cross-section or thickness consistent with strength. The screen perforations are preferably of varying sizes, those of the uppermost screen being largest and those of the other screens decreasing progressively in size toward 50 the bottom.

Sides 6 and I of the separator carry pole pieces l0 and II supporting electromagnetic coils l2 and i3 which are connected in circuit with any suitable source of energizing current. Hence sides 6 and l of the separator, poles l0. and H, and

screens l to 5 inclusive, all of which are composed of magnetic material, constitute the core of the electromagnet and current passing through coils l2 and I3 of said electromagnet sets up a magnetic flux which passes through the screens. Since sides 8 and 9 of the separator are composed of non-magnetic material there will be a concentration of magnetic flux on the screens.

Screens l to 5 are agitated by any suitable vibrator such as electrical vibrator l4 having an armature connected to stem [5 which is hinged or otherwise secured to the screens as shown in Fig. 1. Energization of vibrator l4 causes the screens to vibrate simultaneously at any desired frequency. This vibration facilitates screening of the pulverulent material which is poured on the uppermost screen I containing the largest perforations and passes through the successive lower screens into hopper l6. During the screening operation electromagnetic coils l2 and 13 are energized and magnetic particles contained in the pulverulent material are attracted to one or another of the magnetized screens and adhere thereto while the non-magnetic material passes through. After the non-magnetic material has passed through the screens and been removed from the hopper electromagnets l2 and 13 are deenergized and the magnetic particles are thereupon released by the screens and separately discharged, the screens continuing to vibrate as before.

'Hopper [6 has branched discharge chutes l1 and I8 and pivoted gate l9 for selectively connecting said chutes to the bottom of the hopper. Gate I9 is controlled by electromagnet 20 which is adapted to be energized to move the gate in one direction and by spring 2| which moves the gate in the opposite direction when electromagnet 20 is deenergized. In Fig. 1 electromagnet 20 is energized and gate I9 is swung into position opening chute I1 and closing chute Hi. In this position the non-magnetic material passes through chute l1 into any suitable recep-f tacle. When electromagnet 20' is deenergized gate I9 is moved to the dotted line position in Fig. 1 under tension of spring 2|, closing chute l1 and opening chute I 8. At the same time electromagnets. l2 and I3 are deenergized, freeing the magnetic particles from the screens as previously described, permitting them to be shaken through the screens into hopper Hi from which they pass by chute l8 into any suitable receptacle. The separator of Figs. 1 and 2 is best suited for the magnetic separation of materials which have previously been screened and in this form of the invention all the particles are capable of passing through all-the screens, those of finer mesh serving to contact and retain the finer magnetic particles which have been carried through the higher screens of larger mesh with the non-magnetic materials. Figs. 3 and 4 show another form of the invention which combines sizing and magnetic separation in one operation.

The machine of Figs. 3 and 4 has a multiple deck screen comprising upper screen 23 and lower screen 24 which are stretched in a frame having two opposite sides 25 and 26 composed of magnetic material and the other two connecting sides preferably composed of non-magnetic material. Sides 25 and 26 form part of the core of electromagnets 21 and 28, the magnetic flux passing through and being concentrated on the screens as previously described. The screen frame is mounted in the upper end of hopper 29 with the screens at any suitable angle to the horizontal such that materials which are too large to pass through the screen perforations will be carried by gravity, assisted by the vibration of the screens, over the lower edges of the screens and into receptacle 30.

The mixed magnetic and non-magnetic materials to be sized and magnetically separated are fed through spout 3| which spreads them evenly upon the upper edge of uppermost screen 23. This screen has larger perforations than lower screen or screens 24, it being understood that I do not limit myself to a double-decked screen as any desired number of superposed screens may be employed; The screens are constantly agitated by vibrator 32 which is connected to the screens in any suitable manner as previously described. The material progresses along the surface of screen 23 which attracts and holds magnetic particles and allows non-magnetic particles up to a predetermined maximum size to pass through onto screen 24. Non-magnetic particles which are too large to pass through the perforations of screen 23 pass over the lower edge of said screen and fall into receptacle 30. Screen 24 effects a further sizing of non-magnetic materials and also attracts and retains magnetic particles which have escaped through screen 23. Non-magnetic particles which are too large to pass through the perforations of screen 24 pass over the lower edge of said screen and fall into receptacle 30. This receptacle is preferably divided into two or more compartments as by bafile or bafiies 33 extending up to the screen frame and dividing the separated streams of material as shown in Fig. 3, the number of compartments in receptacle 30 depending upon the number of screens in the machine. The magnetic and nonmagnetic materials capable of passing through all the screens are removed from hopper 29- through gate-controlled chutes as previously described, the non-magnetic materials being collected in one compartment of receptacle 34 and the magnetic particles being collected in the other compartment of said receptacle. Magnetic particles which are too large to pass through the screens will pass over the lower edge thereof when electromagnets 21 and 28 are deenergized and may be collected in any suitable receptacle.

In all forms of the invention the material, as it passes over and through the several magnetized screens which conduct the magnetic flux from the pole on one side of the machine to the pole on the other, is given many opportunities to come in direct contact with magnetic surfaces of high flux density. This high flux density on the screen surfaces is produced by eliminating magnetic losses through the use of closed circuits embodying conductive members of small crosssection. It is well known that magnetic flux is concentrated at the points of minimum surface and for this reason conductive members of the smallest possible gauge are preferably used.

Since the first screen receives the initial contact with the feed, this surface preferably has openings greater than the second magnetic surface, each succeeding surface having smaller openings in order that the iron-bearing impurities may be equally distributed over all the surfaces and not cause clogging of the screen perforations with magnetic impurities.

When coarser mesh screens are used, the effi- 'ciency can be increased by the use of vertical steel points or pins at right angles to the magnetic surfaces and forming a part of the magnetic screen surface. By the use of these points, the feed is given a longer period of contact with the magnetic surfaces and the ability of the magnetic screen surface to retain iron-bearing impurities is also further increased.

In all forms of the invention, the number of magnetic screens may be increased or decreased, depending upon'th'e amount of iron-bearing impurities in the material to be treated and the iron content desired in the finished product. As the number of magnetic surfaces increases, the feed is given a greater number of opportunities to come in direct contact with the magnetized screen surfaces, thus affording more opportunities for the removal of iron-bearing impurities.

The application of my invention to the separa-- tion of ground or pulverized materials containing free metallic iron has shown its superiority over other magnetic separators. As an example, when separating ground minus 200 mesh material containing a substantial amount of free metallic (abraded) iron as well as garnet and biotite mica, resulting in an average F6203 content of 0.30%, by treatment on the magnetic separating screen, the F6203 content of the feed is reduced to 0.10%, thus producing a saleable commercial product which would otherwise be wasted because of the impossibility of treating such finely ground materials on other magnetic separating apparatus.

With this invention I have been able to obtain an efficiency of separation not heretofore possible on finely ground products, for the reasons that First-the feed is continually broken up or dispersed and maintained in such condition in magnetic fields to allow/the individual particles or grains to be in direct contact with the magnetic surfaces.

Secondthe large number of magnetic points of contact and the use of successive magnetic treatments insures the separation of all traces of magnetic materials from. those that are nonmagnetic.

It is not my intention to limit myself to the form and construction of the devices herein illustrated and described since many changes may be made therein without departing from the spirit of the invention. 4

The invention claimed is:

1. A magnetic separator comprising a plurality 70' of superposed magnetic screens having perforations decreasing progressively in size from the top toward the bottom and being arranged to sift pulverulent materials of given size from one screen to another, means for vibrating said screens .to discharge non-magnetic material therethrough and bring magnetic particles into direct adhering contact therewith, means for demagnetizing said screens to release said magnetic particles and permit them to pass through said screens, and means for separately collecting magnetic and non-magnetic materials discharged through said screens.

2. A magnetic separator comprising a hopper, a plurality of superposed sloping screens supported thereby and arranged to sift pulverulent materials of given size from one screen to another and thence into said hopper, the lower edges of said screens being unobstructed to discharge materials larger than a given size over the edges of said screens outside said hopper, means for magnetizing said screens, means for vibrating said screens to discharge non-magnetic material and bring magnetic particles into direct adhering contact with the magnetized surfaces of said screens, means for demagnetizing said screens to release said magnetic particles and permit them to pass into said hopper or over the edges of said screens according to size, and means for separately discharging the magnetic and non-magnetic materials from said hopper.

3. A magnetic separator comprising a plurality of superposed magnetic screens adapted to pass material progressively from top to bottom and being arranged to sift pulverulent materials of given size from one screen to another, means for vibrating said screens to discharge non-magnetic material therethrough and to bring magnetic particles into direct adhering contact therewith,

means for demagnetizing said screens to release said magnetic particles and to permit them to pass through said screens, separate chutes for the magnetic and non-magnetic particles, means to normally direct the non-magnetic particles into one of said chutes, and means operable in conjunction with the demagnetization of said screens to direct the magnetic particles which have passed through said screens into the other of said chutes.

4. A magnetic separator comprising a hopper, a sloping screen supported thereby and arranged to sift pulverulent material of given size into said hopper, the lower edges of said screen being unobstructed to discharge materials larger than a given sizeover the edges of said screen outside said hopper, means for magnetizing said screen, means for vibrating said screen to discharge nonmagnetic material and bring magnetic particles into direct adhering contact with the magnetized surfaces of said screen, means for demagnetizing said screen to release said magnetic particles and permit them to pass into said hopper or over the edges of said screen according to size, separate chutes adapted to receive the magnetic and nonmagnetic materials from said hopper, a gate normally directing the non-magnetic materials into one of said chutes, and means responsive to the demagnetization of said screen to actuate said gate to direct the magnetic material which has 30 passed through said screen into the other of said chutes.

JOSEPH H. WEIS. 

